豫东防护林的营造,其目的在于防风固沙,扩大耕地面积,稳定和不断提高农作物的产量。几年来的实践証明,这些良好的效益已逐漸显示出來了。据观察、在防护林的作用下,风速降低了20％左右,空气湿度增高了2—4％,蒸发量平均 The construction of Yungdong shelterbelt aims at windbreak and sand fixation, expanding cultivated land area, stabilizing and continuously increasing the output of crops. Years of practice have proved that these good benefits have gradually emerged. It is observed that in the role of shelterbelts, the wind speed decreased by about 20%, the air humidity increased by 2-4%, the average evaporation